Disubstituted tolans and preparation thereof

ABSTRACT

Tolans are provided having the formula   IN WHICH EACH OF R and R1 is an alkyl or alkoxy group, the sum of the number of carbon atoms in R and R1 being at least 2 but less than 21, provided that when R and R1 are both alkoxy or both alkyl the sum of the number of carbon atoms is at least 9 but less than 21 and further provided that each of R and R1 has at least 1 but less than 11 carbon atoms. The tolans of the invention are useful as nematics in diverse fields such as thermometry, display and television. The tolans also are useful in forming birefringent plates with fixed or variable delay, as solvents for polarising filters and as anisotropic solvents, especially in optical spectroscopy and nuclear magnetic resonance.

Elite tes atet [191 ,1 acques Dcc.9,1975

[ DISUBSTITUTED TOLANS AND PPARATION THEREOF [75] Inventor: Jean Jacques, Paris, France 22 Filed: June 1, 1972 21 Appl. No.: 258,859

[30] Foreign Application Priority Data June 2, 1971 France 71.19929 Nov. 19, 1971 France 71.41515 [52] US. Cl 260/612 R; 252/299; 252/300; 252/408; 260/613 R; 260/668 R; 350/160 LC [51] Int. Cl. C07C 43/20; C07C 43/22 [58] Field of Search 260/612 R, 613 A, 613 R, 260/613 D, 668 R [56] References Cited UNITED STATES PATENTS 3,742,067 6/1973 Sterger et a1. 260/613 A Primary ExaminerNorman Morgenstern Attorney, Agent, or FirmArmstrong, Nikaido & Wegner [57] ABSTRACT Tolans are provided having the formula in which each of R and R is an alkyl or alkoxy group, the sum of the number of carbon, atoms in R and R being at least 2 but less than 21, provided that when R and R are both alkoxy or both alkyl the sum of the number of carbon atoms is at least 9 but less than 21 and further provided that each of R and R has at least 1 but less than 11 carbon atoms. The tolans of the invention are useful as nematics in diverse fields such as thermometry, display and television. The tolans also are useful in forming birefringent plates with fixed or variable delay, as solvents for polarising filters and as anisotropic solvents, especially in optical spectroscopy and nuclear magnetic resonance.

17 Claims, No Drawings DISUBSTITUTED TOLANS AND PREPARATION THEREOF This invention relates to tolans, to their preparation and to certain mixtures thereof.

The interest which is now being shown in liquid crystals and the nematic phases in particular, is due to their application in the most diverse fields (thermometry, display and television). Numerous recent articles have reported the results achieved and the vistas opened up (see in particular: Phase Zero, No. 2, page 39 and Telonde 1971, page 1).

The factors which limit the possible uses of the nematics remain the generally high temperature of the mesomorphic region (nematics melting below 50C are still exceptional), the chemical instability of products with satisfactory physical characteristics (Schiffs bases, for example, are very easily hydrolyzable), and finally the colour of numerous interesting substances.

One object of the present invention is to produce new substances which give rise to liquid crystals, which are stable and colourless and which have a very low vapour pressure. Another object is to provide substances of this type which, either in pure or admixed form, have mesomorphic properties at relatively low temperatures or even at ambient temperature.

According to the present invention there is provided a tolan having the general formula in which each of R and R is an alkyl or alkoxy group, the sum of the number of carbon atoms in R and R being at least 2, provided that when R and R are both alkoxy or both alkyl the sum of the number of carbon atoms therein is at least 9, each of R and R having from 1 to 10 carbon atoms.

The substances may therefore be symmetrical diethers, unsymmetrical di-ethers, unsymmetrical compounds which are p-alkyl-p'-alkoxytolans or symmetrical or unsymmetrical compounds which are p,p-dialkyltolans.

The symmetrical di-ethers are stable nematics when the radical R has more than carbon atoms, but the transition temperatures from the crystalline state to the mesomorphic state are, in general, higher than 100C; however, this temperature is 92C for di-(para-noctyloxy)tolan.

As for asymmetrical di-ethers, they demonstrate nematic properties when the total number of carbon atoms in R and R is greater than 9. When the total number of carbon atoms is 10, 11 or 12, and the carbon chains in R and R are straight, the transition points from the crystalline state to the mesomorphic state are grouped within the range of 80 to 100C, the mesomorphic intervals being about to C.

Particularly interesting compounds are the p-alkylp-all oxytolans for which the total number of aliphatic carbon atoms exceeds 2, in particular those for which this number is 4 to 12. Amongst these, p-n-nonyl-p'- mcthoxytolan, p-n-octyl-p'-ethoxytolan, p-n-propyl-p' n-heptyloxytolan, p-n-heptyl-p-n-propoxytolan, p-

methoxy-p-n-pentyltolan and p-methoxy-p'-heptyltolan have transition points from the crystalline state to the mesomorphic state at temperatures lying between 40 and 50C.

The p,pdi-alkyl-tolans do not, in general, possess a stable nematic character; however the mixtures obtained from these tolans and from tolans bearing at least one alkoxy group having 1 to 10 carbon atoms on one of the phenyl nuclei may have a stable nematic character at a temperature range lower than 50C.

, The invention includes mixtures of tolans such as defined above and, in particular, eutectic mixtures, which have the advantage of possessing a. transition point from the solid to the mesomorphic state lower than that of the constituent which has the lower transition point, the transition temperature from the mesomorphic state to the liquid state being intermediate between those of the pure constituents Leaving aside certain conditions which will be mentioned below, it is possible to calculate the fusion temperature of a mixture of n constituents and the composition of the eutectic mixture (minimum fusion temperature). The classical formula of Schroder Van Laar establishes a relation between the temperature T the fusion enthalpy AH of a pure constituent and x the molar fraction of this constituent in a mixture melting at a temperature T (R being the constant for a perfect gas).

The values (Al-I of the fusion enthalpies necessary for the calculation which follows are easily obtained, for example by calorimetry using commercially available apparatus.

The mixture with the lowest possible fusion point is that for which the sum of the molar fractions of all the constituents is equal to 1.

There will now be given, by way of example, the calculation of the composition and the fusion point of a binary mixture.

This calculation has been performed by a graphic method for the two compounds possessing the following characteristics.

T AH

a) 4-methoxy-4'-hepty1tolan 39 5.1K cal/mole b) 4-ethoxy-4'-octyltolan 47.5 4.1K cal/mo] 40% by weight of p-octyl-p-ethoxytolan 36% by weight of p-hepty -p-propoxytolan 24% by weight of p-nonyl-p-methoxytolan melting at 20C and remaining nematic up to 65C.

The application of the foregoing method is no longer valid in cases in which the constituents of the mixture form solid solutions and addition compounds amongst themselves. In a general fashion, the departure of the behaviour of the constituents from the ideal thermodynamic behaviour may introduce a certain divergence between the calculated values and experimental results.

It is possible, according to the invention, to prepare the new tolans by dehydrohalogenation, accompanied by intramolecular rearrangement, from 1,1-diphenyl-2- halogenoethylenes having the general formula CH.Hal

in which Hal signifies a halogen atom, more especially a bromine atom.

It is advantageous to carry out the fusion reaction of the 1,1-diphenyl halogeno-olefin with a tertiary-butylate of an alkali metal, more especially of potassium. The use of a diluent is not necessary.

Instead of beginning with the 2-halogeno compound, it is possible to begin with the crude halogenation product, in particular with the crude bromine addition product of the corresponding 1,1-diphenyl-ethylene without isolating the said halogenated compound.

The following examples illustrate the nature of the invention; the temperatures are all in degrees centigrade.

EXAMPLE 1 a. p-Ethoxy bromobenzene (general method described by Carter and Hey, Journal of the Chemical Society 1948, page 152) A phenate solution is prepared in a 1 liter rotavapor flask from 200 ml of absolute ethanol, 4.6 g (0.2 M) of sodium and 34.6 g (0.2 M) of p-bromophenol. A solution of 17 ml (0.2M) of ethyl bromide in 25 ml of absolute ethanol is then added. The addition requires 30 minutes. It is then refluxed for one hour and 5 ml (0.05 M) of ethyl bromide dissolved in 5 ml of ethanol are added. Refluxing is continued for 3 hours during which sodium bromide precipitates.

After evaporation of the ethanol in the rotavapor 100 ml of water are added. The aqueous phase is extracted with ether. The ethereal phase is washed with water, then with dilute hydrochloric acid, then with salt water and dried over sodium sulfate.

After evaporation of the ether, the crude product is distilled. 35.5 g of p-etoxybromobenzene are collected. Bpt =109f/16 mm.

b. p-octyloxyacetophenone.

7.9 g (0.05 M) of the phenate of p-hydroxyacetophenone, 14.2 g (0.05 M) of n-octyl tosylate and 100 ml of dimethylformamide are mixed. The mixture is heated at 1 on an oil-bath for 16 hours. Water is then added and the product extracted with ether. The ethereal phase is washed with 2N soda, water, dilute hydrochloride acid, and finally with salt water. After drying over sodium sulfate, the ether is evaporated and 12.4 g of crude product (theoretical quantity) is recovered. The ketone is distilled at low pressure. Bpt l54/1 mm. 10 g are recovered; the yield is thus 81%. Instead of octyl tosylate, octyl bromide may also be used.

c. p-Ethoxy-p-octyloxydiphenylethylene:

A magnesium compound is prepared from 0.15 g (0.006 M) of magnesium, 1.26 g (0.006 M) of p-ethoxlene thus obtained melts at 108.

d. p-Ethoxy-p-octyloxytolan.

To a solution of 400 mg of p-ethoxy-p octyloxydiphenyl ethylene obtained as described in c in 30 ml of ether, bromine is added until the colour thereof persists. The ethereal solution is washed with N soda, water, dilute hydrochloric acid and salt water. After drying and evaporation of the ether, the residue is heated with 500 mg of dry potassium t-butylate at 150 (oil bath) for 2 hours. The reaction mixture is treated with dilute hydrochloric acid and the aqueous phase is extracted with ether. After evaporation of the ether the recovered tolan is twice recrystallized from absolute alcohol. 240 mg are obtained.

The p-ethoxy-p-octy1oxytolan thus obtained has a transition point at 91 for the change from the solid to the mesomorphic state and 1 13 for the change from the mesomorphic state to the liquid state.

Instead of brominating with bromine in an ethereal solution, it may also be done with phenyltrimethyl ammonium bromide (PTT) in tetrahydrofuran. As a general rule, the dibromide obtained (which may be a mixture of cis and trans isomers when the two benzene nuclei carry different groups) may be directly dehydrobrominated by a strong base (sodium amide, alcoholates, etc). This re-arrangement is known as the Fritsch-Buttenberg-Wiechell (1894) re-arrangement (see The Merck Index, 8th Edition (1968), page 1168, for recent references).

The conversion of the diphenylethylenes to the tolans, as has been seen under d, may be carried out without isolation of the product of the intermediate stages.

EXAMPLES 2 to 30 By proceeding as under b in Example 1 from the appropriate derivatives of 1,1-diphenyl-ethylene, the tolans are obtained which are identified in the following table by the different groups recorded for the symbols R and R and the transition temperatures between crystalline forms (C C and (C C from the crystalline state to the mesomorphic state (C N) and from the mesomorphic state to the liquid state (N L). The bracketed temperatures correspond to metastable transitions.

The diphenyl-ethylenes which can be used as starting a of Example 1, using, if desired, an alkyl iodide or materials are also new substances, which can be prechloride instead of an alkyl bromide.

pared as described in part c of Example 1; the melting For those p-alkoxy-bromobenzenes which are new, point of those for which it has been possible to make 5 there are appended the boiling points as well as the the determination appear in the following table. yield in their preparation c 11 o 1ar Bpt 145/2o mm Yield 57% (from c a c1) 11 O Br Bpt 126 mm Yield 90% (from c 11 Br) TABLE I1 0 The corresponding figures appear below for those of R Melting point the alkoxy-actophenones which are new and Wl'llCh may be obtamed as descnbed 1n part b of Example 1. C330 n-c,,H ,o 107 C nC H O 105 c 11,o nC 11 0 110 H 0 M c,H ,o n-Clliib 108 9 1 C0333 Pt 32 gz1 1 C- 11 0 103 n 4H 0 nC H ;0 106 0 1 n-C H O 00.011 Mpt 35.5 n c,11,,o n c,11,,o 116 nC,,H 7O nC H 0 104 0 1Hl50 nC1Hl,-,O 108.5 4 1 P nC H O nC H O 106 CH, n c,11,,,o 69 1 Z "-5 Among the tolans described above in Table l the ic, H1 ::C:H:;O 6 compounds possessing the lowest transition temperan C,H,,0 nCflHm 44 tures (T) from the crystallme to the mesomorphlc state cH ,o n c,11, 46 CHHO are the followmg. CHHO nC-,H, 1 about 35 (EH50 67 TABLE 111 1-1, n c,,11,,o 59 A a p cptyl p methoxytolan T 39 nC11H nc'iHmo B p-heptyLp'-propoxytolan T 41 C p-nonyl-p-methoxytolan T 41 D p-pentyl-p-methoxytolan T 43 6 1 E -()c1 1- '-ethox tolan T=47.5 r 1 P y P y The p alkyloxy bromobenzenes used as sta t ng ma F p pemyl p, pemyloxytolan T=48 5 terials are obtained by proceeding as indicated in part The present invention also relates to mesomorphic mixtures which are mixtures of tolans. The most interesting mixtures are often binary mixtures of p-alkyl-palkoxytolans amongst themselves or of p-alkyl-p'- The tolans described in the present application and their mixtures may be employed not only in the fields application in which liquid crystals are used but also in forming birefringent plates with fixed or variable delay,

alkoxytolans and p,p'-di-alky1tolans. as solvents for polarising filters and as anisotropic sol- Particularly interesting mesomorphic mixtures are vents, especially in optical spectroscopy and nuclear those enumerated below, the constituents (tolans listed magnetic resonance. above in table 111) being preferably present in substan- What I claim is: tially equimolecular quantities 10 l. A tolan of the formula Nematic over the a range (inclusive of 1 Mixture boundaries) R QCIC-QR B D 0 59 A F 7 57 F wherein R and R are unlike alkoxy groups, wherein 2: g 2;: each of R and R has at least 1 but less than 1 1 carbon A D 0 I atoms and the total number of the carbon atoms in R and R is more than 9 and less than 13.

2. A tolan of the formula RQCEC 0 1 wherein R is an n-alkyl group and R is an n-alkoxy group, wherein each of R and R has at least 1 but less than 1 1 carbon atoms and the total number of the carbon atoms in R and R is more than 3 but less than 13.

3. The compound of claim 2 of the formula 4. The compound of claim 2 of the formula 5. The compound of claim 2 of the formula 6. The compound of claim 2 of the formula CH CH OQC c QCHZCHZCHZCHZCHZCHZCHZCHIB 7. The compound of claim 2 of the formula 8. The compound of claim 2 of the formula 9. The compound of claim 2 of the formula 10. The compound of claim 2 of the formula A mixture obtained from a p-alkyl-p'alkoxytolan and 20 a p,p-di-alkyltolan, the constituents of which are not of a stable nematic character, and which is of a particularly interesting nature, is the following:

Range over which the mixture has a stable nematic character Constituents p-butyl-p'-methoxytolan (Mpt 46) p,p-diheptyltolan (Mpt 39.5) 15 11. The compound of claim 2 of the formula 12. The compound of claim 2 of the formula 13. The compound of claim 2 of the formula 14. The compound of claim 2 of the formula 15. The compound of claim 2 of the formula CH CH O Q C C QCIECH CH 16. The compound of claim 2 of the formula 17. The compound of claim 2 of the formula CH E CH3 cH cH cH cH cH cH 0-c CGCH CH 

1. A TOLAN OF THE FORMULA
 2. A TOLAN OF THE FORMULA
 3. The compound of claim 2 of the formula
 4. The compound of claim 2 of the formula
 5. The compound of claim 2 of the formula
 6. The compound of claim 2 of the formula
 7. The compound of claim 2 of the formula
 8. The compound of claim 2 of the formula
 9. The compound of claim 2 of the formula
 10. The compound of claim 2 of the formula
 11. The compound of claim 2 of the formula
 12. The compound of claim 2 of the formula
 13. The compound of claim 2 of the formula
 14. The compound of claim 2 of the formula
 15. The compound of claim 2 of the formula
 16. The compound of claim 2 of the formula
 17. The compound of claim 2 of the formula 